Heating apparatus

ABSTRACT

Heating apparatus is provided for producing hot water or warm air which comprises an air blowing device, a compact combustion apparatus having a high load factor in which a combustion catalyst is employed, and a compact heat exchanger which is wellmatched to the combustion apparatus, whereby high efficiency and high performance in the combustion and heat exchange processes are achieved.

United States Patent 91 Ito et al.

[ 1 Jan. 9, 1973 [54] HEATING APPARATUS [75] Inventors: Toshio Ito; Tamotsu Nomaguchl; Norikazu Tabata, all of Amagasaki, Japan [73] Assignee: Milsuhlshi Electric Tokyo, Japan [22] Filed: Aug. 14,1970

[2]] App1.N0.: 63,855

Corporation,

[30] Foreign Application Priority Data Aug. 26, 1969 Japan ..44/67454 Sept. 4, 1969 Japan ..44/70l64 Nov. 10, 1969 Japan ..44/89894 [52] US. Cl. ..263/l9 R, 110/97 D, 431/353 [51] Int. Cl ..F23l 1/00 [58] Field of Search ..437/326, 328, 347, 353, 158; 263/19; 110/97 [5.6] References Cited UNITED STATES PATENTS 3,273,621 9/1966 Childree ..263/l9 A 3,380,410 4/1968 Venable ..110/97 2,601,167 6/1952 Navarro ..l10,97 2,369,995 2/1945 Arnold ..1 10/97 2,907,382 10/1959 Mcllvaine ..431/l58 X 2,425,630 8/1947 McCullum ..431/347 X Primary Examiner-Edward G. Favors Attorney-Oblon, Fisher & Spivak [57] ABSTRACT Heating apparatus is provided for producing hot water or warm air which comprises an air blowing device, a compact combustion apparatus having a high load factor in which a combustion catalyst is employed, and a compact heat exchanger which is well-matched to the combustion apparatus, whereby high efficiency and high performance in the combustion and heat exchange processes are achieved.

11 Claims, 6 Drawing Figures PATENTEDJAM 9197a 3.709.473

SHEEI 1 BF 2 FIG.2

INVENTORS 765Hl0 ITo fimoTau NOMAGUCHI Nom mzu TAB/WA 'BY 6 51 57, 51AM u ATTORNEYS Pmmmm 9 ma 3.709.473

SHEET 2 UF 2 FIG?) Gas INVENTORS Tsmo ITO TAMOTSU NOMAGUCHI V b Nomm'zu HBATA 01%, MMQ /g ATTORNEYS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to a heating apparatus having a heat exchanger, and more particularly to a heating apparatus for producing hot water or warm air.

2. Description of the Prior Art In conventional heating systems used for water-heating and room heating, the combustion of the fuel gas usually occurs in an open space, simply drawing on the ambient, or surrounding, air for supporting the combustion, and heat exchange is caused by natural convection currents. In these types of heating systems, complete combustion cannot be achieved without drawing in an. excessive quantity of secondary air, in terms of the chemical equivalency of air and fuel gas to provide the necessary, or primary, air for burning the fuel.

Certain disadvantages are found in the conventional heating systems described hereinabove, namely, for example, that the temperature of combustion gas is decreased, the combustion time is prolonged, and a large space is required for combustion to draw in the aforedescribed quantity of excess air. In order to draw a large excess of secondary air by natural convection into the conventional heat exchanger, it is necessary to minimize the pressure loss, and also a large space for heat exchanging must be provided, because of the low heat exchange coefficiency caused by the low temperature of the combustion gas. Accordingly, another disadvantage is that a large space and body unit .are required for the conventional heating systems heretofore used for water-heating and room-heating.

SUMMARY OF THE INVENTION This invention therefore aims at providing an improved heating apparatus for producing hot water or warm air wherein a combustion apparatus is arranged such that air being forceably introduced from the outside and fuel gas being provided under suitable pressure are injected thereinto by being divided into as many portions as possible so as to enhance the fuel-air mixing efficiency by a resultant ejector effect, and in which there is provided a catalyst for producing on its surface a large amount of active molecules effective for execution of chain reactions of combustion, thereby to obtain complete combustion of extremely high stability, and further having a heat exchange device arranged such that a large pressure loss results during passing of the combustion gas therethrough, the device preferably having many ducts or fins provided downstream of the catalyst over which cool water or air may be passed to produce the desired hot water or warm air.

It is an object of this invention, therefore, to provide a compact heating apparatus in which complete combustion is achieved with the rate of air-to-fuel gas being approximated to the stoichiometrically determined value, thus allowing a reduction of combustion space and thereby achieving a resultant enhancement of combustion gas temperature and, in addition, permitting a reduction of heat exchange space, so that the size of the heating apparatus is reduced for total calorific value being provided.

It is another object of this invention to provide a heatingapparatus in which high coefficiency of heat exchange is achieved by enhancing the combustion gas temperature.

It is an additional object of this invention to provide a heating apparatus for producing hot water in which high thermal efficiency is provided.

A further object of this invention is to provide a heating apparatus for producing warm air in which high thermal efficiency is provided.

A still further object of this invention is to provide a heating apparatus in which effective heat exchange is provided prior to introducing a combustion gas in a heat exchanger, so that the load of the heat exchanger itself is lightened.

Still a further object of this invention is to provide a compact heating apparatus in which pressure losses in both a combustion chamber and a heat exchanger are substantially similar.

Yet another object of this invention is to provide a heating apparatus in which stabilized and quiet combustion is provided.

Still yet another object of this invention is to provide a heating apparatus in which a stable starting point for ignition is provided, so as to thereby obtain stabilized and quiet combustion.

BRIEF DESCRIPTION OF THE DRAWINGS These and other objects as well as further attendant features and advantages of the present invention will be more readily appreciated as the same becomes better understood from the following detailed description when considered in connection with the accompanying drawings, wherein:

FIG. 1 is a sectional view of a conventional heating apparatus for producing hot water;

FIG. 2 is a sectional view of an embodiment of a heating apparatus for producing hot water formed according to the teachings of this invention;

FIG. 3 is a sectional view of an embodiment of a heating apparatus for producing warm air formed according to the teachings of this invention;

FIG. 4 is a sectional view of combustion apparatus which is a part of another embodiment of this invention;

FIG. 5 (a) is a partial enlarged view of the mixing plate shown in FIG. 4; and

FIG. 5 (b) is a cross-sectional view taken along the line V-b V-b ofFIG. 5 (a).

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, wherein like numerals designate like or corresponding parts throughout the several figures, and more particularly to FIG. 1 thereof, a conventional heating apparatus for producing hot water is shown, in which the reference number 1 indicates a gas burner having a fuel gas inlet pipe 2, a primary air suction nozzle 3 and a combustion nozzle 4. The reference number 5 indicates a cylindrical water jacket positioned at one end of the burner 1 through'which water is fed from a cold water inlet pipe 6 in a lower part thereof to a hot water outlet pipe 7 in the upper end. An annular space between the gas burner 1 and the water jacket 5 provides an inlet 8 for drawing in secondary air. l-leat exchanging fins 9 which are thermally connected with a water jacket 10 through a fin cooling pipe are disposed in the end of the cylindrical jacket 5 opposite the burner 1 and spaced therefrom to define therebetween a combustion chamber 1 1.

In the operation of the heating apparatus shown in FIG. 1, the fuel gas is fed through the gas inlet pipe 2 under pressure and is mixed by drawing primary air 7 through the nozzle 3. The mixture is ignited and flame is initiated at the outlet of combustion nozzle 4 whereby combustion is provided in the combustion space 11 with secondary air being drawn by natural convection current through the gap 8. The combustion gas is cooled as it passes over the heat exchanging fins 9 and pipes 10 while water in the jacket 5 is heated by the hot combustion space it encompasses.

The disadvantages of such conventional heating apparatus as described hereinabove for producing hot water are, as already stated, the requirement of a large amount of secondary air in the combustion, whereby combustion gas temperature is decreased and combustion time is prolonged, and the requirement of a large space accommodating the combustion. Additionally, it is necessary to minimize pressure loss for drawing in large quantities of secondary air by natural convection current and it is required that a large space be provided for heat exchanging purposes, because of the low heat exchange coefficiency due to the low temperature of the combustion gas.

In FIG. 2, there is shown a heating apparatus for producing hot water embodying the teachings of this invention, in which the reference number 12 indicates an air blower, such as one having blast pressure of 10mm water head, and the reference numeral 13 indicates a cylindrical combustion chamber shell which is tapered at one end and is preferably made of refractory case metal. The air blower 12 is connected to the tapered end of the cylindrical outer shell 13 and an air flow-dividing plate 14, which is illustrated as a disc positioned in the same end of the shell 13 with a plurality of holes formed therein, preferably being made of stainless steel, divides the air flow being fed through the air blower 12.

A plurality of air ducts 15, formed from cylindrical bodies or pipes fitted in each of the holes in the flow dividing plate 14, also preferably being made of stainless steel, feed the air divided by the flow dividing plate 14 to an antechamber 16. A mixing plate 17, having a plurality of through holes 18 corresponding to the air ducts 15, each having an inner diameter which is slightly larger than the outer diameter of the respective corresponding air duct such that an annular space 19 is formed there between, is disposed between the dividing plate 14 and the antechamber 16. Each air duct or pipe 15 is positioned in the corresponding hole 18 of the mixing plate 17 in such a manner that the outlet of each duct is disposed intermediate the length of its respective hole 18. The mixing plate 17 is a heat insulating disc which may be made of alumina, zirconia or the like.

Fuel gas, such as, for example, city gas or LP gas, or a mixture of fuel gas and primary or preliminary air, is supplied from an inlet port 20 into the space between the dividing plate 14 and mixing plate 17. A catalyst 21 is illustrated as being a disc positioned in the shell 13 downstream of the mixing plate 17 having a plurality of capillaries 22 therethrough, and preferably is made of a porous high-purity metal oxide such as about percent by weight of alumina (A1 0 zirconia, magnesia or the like. The space between the mixing plate 17 and the catalyst 21 comprises the antechamber 16. Another space 23 on the downstream side of the catalyst disc 21 is for completing chain reactions of combustion.

A heat exchanger 25 is provided downstream of the combustion space 23 and is made of, for example, stainless steel, copper or the like. The exchanger 25 has a plurality of pipes 26 therein through which the high temperature combustion gas is passed. Water is fed from a cold water inlet pipe 27 at the downstream end of the device to a hot water outlet pipe 28 near the combustion space 23.

The operation of the heating apparatus shown in FIG. 2 is as follows:

The air being fed from the blower 12 passes partly through the air ducts 15 and is mixed with fuel gas supplied through the inlet port 20 in the mixing plate 17 and is ignited by a pilot flame 24 in the antechamber 16, whereby combustion is initiated therein through the holes 18. The catalyst 21 is promptly heated by the combustion in the antechamber 16, and full-scale combustion is initiated in the inner surfaces of the capillaries 22 formed in the catalyst 21 approximately ten seconds after ignition, thereby providing an almost flameless combustion. Accordingly, only a small space 23 is required for the slip stream of the catalyst 21, and for supplying uninterrupted heat of a full-scale combustion. The catalyst 21, being made of a refractory heat insulator, such as alumina, functions to produce on its surface, at high efficiency, the active molecules useful in chain reactions of combustion in a hot atmosphere. Combustion in the capillaries 22 proceeds smoothly and promptly, causing additional rise of temperature of the catalyst 21 and thereby increasing its catalytic effect.

In an experiment, the surface temperature of the catalyst 21 reached a level of l,400 C.

The effect of the mixing plate 17 will be understood more clearly from the following detailed explanation given in this connection. Fuel gas is forcibly ejected through the annular space 19 formed between the air ducts 15 and the holes 18, while the air stream simultaneously being fed from the air blower is divided by the flow dividing plate 14 and ejected through the air ducts 15. The ejector effect is produced by the forcible ejection of air into the holes 18 in the mixing plate 17 and provides an extremely efficient admixture of air and fuel gas. In the event, alternatively, where fuel gas, rather than air, is forcibly injected into the holes 18, a similar ejector effect is developed by the fuel gas which also produces excellent admixture of air and fuel gas. As a result, flames start up smoothly from the neighborhood of the inner faces of the holes 18. The mixing plate 17 may be made of the same material as the heat catalyst 21, but metal may also be used to obtain similar stability of combustion. Both the air ducts or pipes 15 and the mixing plate 17 are thereby kept at a relatively low temperature since they are constantly being cooled with pre-combustion gas.

The operation of the heat exchanger 25, being used for producing hot water, is described as follows:

In general, the heat exchange capacity of a heat exchanger is proportional to the difference between combustion gas temperature, tg, and the heat exchanger wall temperature, tw, i.e. (tg tw). In the combustion apparatus of this invention, using the heat catalyst 21, full scale combustion is performed with the rate of air-to-fuel gas being approximated to the stoichiometrically determined value. Accordingly, the combustion gas temperature tg is extremely high, and thereby heat exchange is easily provided and the heat exchanger 25 can be compacted. On heat conductivity from gas to a heat exchanger wall, in this case where heat conduction is given to the walls of a pipe 26, through which the combustion gas is passed, and the amount of combustion gas being passed through the pipes 26 is constant, the smaller the diameter of the pipes 26, the higher is the resultant heat conductivity. In a case where heat conduction is given to the walls of spaced apart plates, through which the combustion gas is passed, and the amount of combustion gas passed through the plates is constant, smaller spacing between the plates similarly results in higher heat conductivity.

Accordingly, the heat conductivity can be increased and the heat exchange may be easily made by providing a pipe of smaller diameter or a smaller spacing between plates, whereby the heat exchanger 25 may be compacted. However, in either of these cases, pressure loss of the heat exchanger 25 is increased. In conventional heating apparatus for producing hot water, it is necessary to decrease pressure loss of the heat exchanger to less than 1 H Omm. However, in the heating apparatus of this invention for producing hot water, the pressure loss of the heat exchanger 25 can be high because the air blower is provided.

In the heating apparatus using the catalyst 21 of this invention, full-scale combustion is performed with the rate of air-to-fuel gas being approximated to the stoichiometrically determined value, thus allowing a reduction in the amount of air being used and thereby achieving a resultant enhancement of combustion gas temperature. Accordingly, as a result, the pressure loss per specific amount of fuel gas can be minimized.

Thus the diameter of each pipe 26 or the space between each of a plurality of plates of the heat exchanger 25 can be smaller than that of conventional heat exchangers, and thereby the heat exchanger 25 can be compacted. It is therefore possible to compact the combustion apparatus and the heat exchanger 25, while providing high pressure loss.

In order to minimize the total size of the combustion apparatus and the heat exchanger, by constantly providing a sum of both the pressure losses which corresponds to the blowing pressure given by the blower, it generally is preferable to have the same pressure loss in the combustion chamber as in the heat exchanger 25. However, the heating apparatus of this invention can be compacted, even though the pressure loss is different in said each part.

In an experimental embodiment, both the flow-dividing plate l4 and the mixing plate 17 had a diameter of 50mm, and the air ducts were prepared by using 37 pieces of steel pipes, each having a length of 15mm, and an outer diameter of 5mm. The mixing plate 17 was perforated to form the holes 18 with diameters of 6mm, and a 10mm thick catalyzer plate 21 having 85 holes of 3mm diameter each was positioned mm behind the mixing plate 17. The heat exchanger 25 had many pipes having diameters of 6mm and being 130mm in length and the blowing pressure of the blower 12 was lOmrn H O. Pressure loss of the combustion apparatus was about 5mm H 0. and pressure loss of the heat exchanger was also about 5mm H O. The volume of the heating apparatus for producing hot water in this experiment was about 1 liter for the combustion apparatus and about I liter for the heat exchanger, or a total volume of 2 liters, and combustion of 6,000 K cal/hr was obtained with a combustion coefficiency of percent.

The arrangement and configuration of the com ponent parts of the apparatus are not restricted to the above embodiment. It is also possible, according to this invention, to obtain extremely compacted heating apparatus for producing hot water by other arrangements of the general combination of the blower, the combustion apparatus using the catalyst, and the heat exchanger having small diameter pipes or small spaces between plate members which produce high pressure loss.

Another embodiment of the heating apparatus being adapted for producing warm air and constructed according to the present invention is shown in FIG. 3. This embodiment is substantially like that shown in FIG. 2, with the exception of the parts described hereinbelow.

Reference numeral 29 indicates a fuel gas inlet part at one end of the device and the reference numeral 30 indicates an air inlet port connected to the blower for supplying air between the dividing plate 14 and the mixing plate 17. Thus the fuel gas inlet port and the air inlet port may be observed as being reversed in the embodiments of FIG. 2 and FIG. 3. Two sheets of catalysts 21 are provided in this embodiment, forming an antechamber 16 behind the mixing plate 17 and a combustion chamber 31 therebetween and another combustion chamber 23 downstream thereof, going to the heat exchanger 25. An end plate 32 is provided on the combustion side of the heat exchanger 25 being connected to the cylindrical shell 13 by a tapered shell 33. The heat exchanger 25 has a plurality of pipes 26 open into chamber 23 over which the air supplied by a blower 3d can be passed, by directly contacting the outer surface of each pipe 26. The reference numeral 35 indicates a combustion exhaust gas outlet duct.

The operation of the heating apparatus for warming the air shown in FIG. 3 is similar to that of FIG. 2, with the exception, however, that the full-scale combustion gas passed through the catalysts 21 and combustion chambers 31 and 23 is exhausted through the heat exchanging pipes 26 connected to the end plate 32, and from the exhaust gas outlet duct 35 to outside the apparatus. The outer shell 13 of the combustion apparatus, the tapered shell 33, the end plate 32 and the heat exchanging pipes 26 are cooled by the air supplied from the blower 34, while the air is simultaneously heated to become warm air, which may be utilized for heating a room. In the combustion apparatus using the catalysts shown in FIG. 3, the full-scale combustion is performed with the rate of air-to-fuel gas being approximate to the stoichiometrically determined value, and thereby the resultant enhancement of combustion gas temperature and catalyst temperature are achieved.

Since a large amount of heat is conducted to the combustion chamber shell 13 by heat radiation from the catalysts 21 and heat conduction of the combustion gas, the heat exchange is accordingly made by blowing the air from the blower 34 over the outer surface of the combustion chamber shell 13. This conduction effect may be increased by providing a fin on the combustion chamber shell 13. Also the heat conduction of end plate 32 is increased by heat radiation from the catalysts 21 and heat conduction caused by contraction and collision of the combustion gas at the time of introducing the gas into the heat exchanging pipes 26.

Accordingly, it is possible to provide a large amount of heat exchange by effectively cooling the end plate 32. Also, it is possible to provide heat exchange from the tapered shell 33. Accordingly, one of the characteristic advantages of this invention is that the load of the heat exchanger can be minimized by providing heat exchange with the air, prior to introducing it in the heat exchanging pipes 26, from the combustion chamber shell 13, the end plate 32 and the tapered shell 33, under the utilization of enhancement of combustion gas temperature and high radiation heat conduction of the catalysts.

In an experimental embodiment, an additional 50 percent of input quantity of heat was obtained as warm air suitable for room heating from the combustion chamber shell 13, the end plate 32 and the tapered shell 33 in the combustion apparatus having two sheets of catalyst, each having a diameter of 70mm, and having a fuel gas input of 3,000 k. cal/hr. The compact and high efficiency heating apparatus for producing warm air of this invention can be constructed with the combination of the blower, the combustion apparatus using the catalyst and the heat exchanger providing the pipes having high pressure loss, by which the air is warmed by the cooling of the combustion chamber shell 13, the heat exchanger and the joint with the blower. Also, fullscale combustion is performed with the rate of air-tofuel gas being approximated to the stoichiometrically determined value to result in the enhancement of combustion gas temperature and catalyst temperature.

Although the heat exchanger having pipes is illustrated, a heat exchanger having a plurality of plates which are arranged in parallel relation with a narrow space therebetween may also be utilized with equal benefits. The heating apparatus for producing warm air of this invention can be used not only for room-heating, but also for plant culture hot-house heating, since the exhaust gas is exhausted to an outer room and the heat exchange coefficiency is quite high. Also it is suitable for using warm air for drying clothing, since no moisture caused by combustion of hydrogen contained in fuel gas is included, inasmuch as the combustion gas is indirectly used by the highly efficient heat exchange.

Any moisture which may be caused by combustion of hydrogen contained in fuel gas is easily condensed and recovered, because of the high efficiency of the heat exchanger. If the air in the room is made dry by using the warm air for room heating, it is possible to provide suitable humidity by feeding this condensed water to an under part of the blower.

Another embodiment of the heating apparatus for 6 producing hot water or warm air constructed according to this invention, is shown in FIGS. 4 and 5. It will be mainly described by referring to the differences between it and the embodiments of FIGS. 2 and 3.

In this embodiment, the combustion chamber shell 13 is divided into two parts, one of which is inserted in the other. In addition, a plurality of air holes 36 are provided in the mixing plate 17. The characteristic advantage of this embodiment is to arrange the mixing plate 17, the ducts 15 and the air holes 36 so that the initiation of flame is smooth and gentle and, also, so that burning flames are stable and make little noise, thus realizing almost soundless combustion.

Referring to FIGS. 5a and 5b, which are partial enlarged views of the mixing plate 17, the operation of the embodiment is stated. In the Figures, the reference numeral 37 indicates the primary flames produced by turbulent mixture of air and fuel and 38 indicates the secondary flames produced by laminar flow type mixture of air and fuel. The ends of the ducts 15 extend beyond the mixing plate 17 by a length substantially equal to the diameter thereof and a plurality of air holes 36 are formed in the mixing plate in a slightly spaced and surrounding relation with these ducts 15. The primary flames 37 are produced in the following manner: when passing through the air holes 36, air is partly turned into a turbulent flow and this turbulent flow, along with a part of the fuel being discharged from the ducts 15, is trapped in a pocket of negative pressure produced at the juncture between the ducts 15 and the mixing plate 17, whereby they become mixed in a turbulent manner. The secondary flames are produced by a gentle laminar flow type mixing of the air and fuel, and their starting point is stabilized by the primary flames. Thus, stabilized flames are produced around the portions of the ducts 15 extending beyond the mixing plate 17, with these protruding portions acting like wicks. As will be understood from the foregoing explanation, the positional relationship between the ducts 15 and the air holes 36 is such that turbulent mixing of the air and the fuel gas is caused at the juncture of the air ducts 15 ,and the mixing plates 17 to give rise to the primary flames which provides a stabilized starting point for the secondary flames.

In all of the embodiments shown in FIGS. 2, 3 and 4, any desired combustion can be obtained by suitably modifying the fuel gas feeding and air feeding ports. In the method for pressuring both the fuel gas and air by forcibly supplying fuel gas and air, pressure of city gas or LP gas can be used and also a blower can be used for providing pressure to the fuel gas. A blower, or if necessary a compressor, can be used for providing the pressure to the air. Moreover, in order to forcibly supply the fuel gas and air, a blower may be provided behind the heat exchanger for drawing them therethrough.

Obviously many modifications and variations are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.

What is claimed as new and desired to be secured by letters patent of the United States is:

1. A heating apparatus comprising:

a combustion chamber shell;

a flow-dividing plate in said shell having a plurality of through holes;

a mixing plate in spaced parallel relation to said flowdividing plate and having a corresponding plurality of through holes;

a catalyst member having a plurality of through capillaries positioned in said combustion chamber shell behind said mixing plate;

an antechamber in said combustion chamber shell between said mixing plate and said catalyst member for containing a mixture of air and fuel gas during preliminary burning thereof;

a plurality of ducts, each having one end connected to a corresponding one of said plurality of holes formed in said flow-dividing plate and the other end disposed in and extending through and beyond a corresponding one of said plurality of holes in said mixing plate and into said antechamber;

heat exchange means behind said catalyst member through which a combustion gas may be passed;

a combustion chamber formed in said shell between said catalyst member and said heat exchange means;

a first inlet port positioned in said combustion chamber shell forward of said flow-dividing plate for admitting either air or fuel gas;

a second inlet port positioned in said combustion chamber shell between said flow-dividing plate and said mixing plate for admitting the other of said air or fuel gas; and

a blower providing pressure to said air corresponding to the pressure loss in said combustion chamber shell and said heat exchanger.

2. The heating apparatus set forth in claim 1 for producing hot water, further comprising means for circulating water over said heat exchange means.

3. The heating apparatus set forth in claim 1 further comprising means for forcing air over said combustion chamber shell and said heat exchange means for producing warm air.

4. The heating apparatus set forth in claim 3 including a plurality of spaced catalyst members in said combustion chamber shell between said mixing plate and said heat exchange means.

5. The heating apparatus set forth in claim 1 wherein the pressure loss of gases in the combustion chamber shell is approximately equal to the pressure loss of the combustion gas in said heat exchange means.

6. The heating apparatus set forth in claim 1 wherein said plurality of holes in said mixing plate each having a greater diameter than the corresponding said other ends of said plurality of ducts extending therethrough, whereby an annular space is provided around each of said other ends of said ducts in said mixing plate.

7. The heating apparatus set forth in claim 1 wherein the other ends of said plurality of ducts project from said mixing plate into said chamber a distance substantially equal to the outer diameter of said ducts, and further comprising a second plurality of holes formed in said mixing plate spaced from and surrounding each of the other ends of said plurality of ducts.

8. The heating apparatus set forth in claim 1 wherein said heat exchange means includes a plurality of pipes through which said combustion gas is passed.

9. The heating apparatus set forth in claim 1 wherein said heat exchange means includes a plurality of spaced parallel plates over which said combustion gas is passed.

10. The heating apparatus set forth in claim 1 wherein said combustion chamber shell is formed in two sections, the end of one being received within the end of the other.

1 l. A heating apparatus for producing warm air comprising:'

a combustion chamber shell;

a flow-dividing plate in said shell having a plurality of through holes;

a mixing plate in spaced parallel relation to said flowdividing plate and having a corresponding plurality of through holes;

a plurality of ducts, each having one end connected to a corresponding one of said plurality of holes formed in said flow-dividing plate and the other end disposed in a corresponding one of said plurality of holes in said mixing plate;

a catalyst member having a plurality of through capillaries positioned in said combustion chamber shell behind said mixing plate;

an antechamber in said combustion chamber shell between said mixing plate and said catalyst member for containing a mixture of air and fuel gas during preliminary burning thereof;

heat exchange means behind said catalyst member through which a combustion gas may be passed;

a combustion chamber formed in said shell between said catalyst member and said heat exchange means;

a first inlet port positioned in said combustion chamber shell forward of said flow-dividing plate for admitting either air or fuel gas;

a second inlet port positioned in said combustion chamber shell between said flow-dividing plate and said mixing plate for admitting the other of said air or fuel gas;

a blower providing pressure to said air corresponding to the pressure loss in said combustion chamber shell and said heat exchanger;

means for cooling said combustion chamber shell and said heat exchange means by blowing air thereover for producing warm air; and

said combustion chamber shell being tapered outwardly for covering the space between said combustion chambershell and said heat exchange means behind said catalyst member, so that the juncture of said shell and said heat exchange means is of greater cross-sectional area than that of said shell. 

1. A heating apparatus comprising: a combustion chamber shell; a flow-dividing plate in said shell having a plurality of through holes; a mixing plate in spaced parallel relation to said flow-dividing plate and having a corresponding plurality of through holes; a catalyst member having a plurality of through capillaries posItioned in said combustion chamber shell behind said mixing plate; an antechamber in said combustion chamber shell between said mixing plate and said catalyst member for containing a mixture of air and fuel gas during preliminary burning thereof; a plurality of ducts, each having one end connected to a corresponding one of said plurality of holes formed in said flow-dividing plate and the other end disposed in and extending through and beyond a corresponding one of said plurality of holes in said mixing plate and into said antechamber; heat exchange means behind said catalyst member through which a combustion gas may be passed; a combustion chamber formed in said shell between said catalyst member and said heat exchange means; a first inlet port positioned in said combustion chamber shell forward of said flow-dividing plate for admitting either air or fuel gas; a second inlet port positioned in said combustion chamber shell between said flow-dividing plate and said mixing plate for admitting the other of said air or fuel gas; and a blower providing pressure to said air corresponding to the pressure loss in said combustion chamber shell and said heat exchanger.
 2. The heating apparatus set forth in claim 1 for producing hot water, further comprising means for circulating water over said heat exchange means.
 3. The heating apparatus set forth in claim 1 further comprising means for forcing air over said combustion chamber shell and said heat exchange means for producing warm air.
 4. The heating apparatus set forth in claim 3 including a plurality of spaced catalyst members in said combustion chamber shell between said mixing plate and said heat exchange means.
 5. The heating apparatus set forth in claim 1 wherein the pressure loss of gases in the combustion chamber shell is approximately equal to the pressure loss of the combustion gas in said heat exchange means.
 6. The heating apparatus set forth in claim 1 wherein said plurality of holes in said mixing plate each having a greater diameter than the corresponding said other ends of said plurality of ducts extending therethrough, whereby an annular space is provided around each of said other ends of said ducts in said mixing plate.
 7. The heating apparatus set forth in claim 1 wherein the other ends of said plurality of ducts project from said mixing plate into said chamber a distance substantially equal to the outer diameter of said ducts, and further comprising a second plurality of holes formed in said mixing plate spaced from and surrounding each of the other ends of said plurality of ducts.
 8. The heating apparatus set forth in claim 1 wherein said heat exchange means includes a plurality of pipes through which said combustion gas is passed.
 9. The heating apparatus set forth in claim 1 wherein said heat exchange means includes a plurality of spaced parallel plates over which said combustion gas is passed.
 10. The heating apparatus set forth in claim 1 wherein said combustion chamber shell is formed in two sections, the end of one being received within the end of the other.
 11. A heating apparatus for producing warm air comprising: a combustion chamber shell; a flow-dividing plate in said shell having a plurality of through holes; a mixing plate in spaced parallel relation to said flow-dividing plate and having a corresponding plurality of through holes; a plurality of ducts, each having one end connected to a corresponding one of said plurality of holes formed in said flow-dividing plate and the other end disposed in a corresponding one of said plurality of holes in said mixing plate; a catalyst member having a plurality of through capillaries positioned in said combustion chamber shell behind said mixing plate; an antechamber in said combustion chamber shell between said mixing plate and said catalyst member for containing a mixture of air and fuel gas during preliminary burning thereof; heat exchange means behind Said catalyst member through which a combustion gas may be passed; a combustion chamber formed in said shell between said catalyst member and said heat exchange means; a first inlet port positioned in said combustion chamber shell forward of said flow-dividing plate for admitting either air or fuel gas; a second inlet port positioned in said combustion chamber shell between said flow-dividing plate and said mixing plate for admitting the other of said air or fuel gas; a blower providing pressure to said air corresponding to the pressure loss in said combustion chamber shell and said heat exchanger; means for cooling said combustion chamber shell and said heat exchange means by blowing air thereover for producing warm air; and said combustion chamber shell being tapered outwardly for covering the space between said combustion chamber shell and said heat exchange means behind said catalyst member, so that the juncture of said shell and said heat exchange means is of greater cross-sectional area than that of said shell. 